Standard practice in the installation of electrical wiring is to attach a connector to a service box and attach a conduit to the connector. The wires being installed are then passed through the conduit, through the connector and into the service box. The purpose of the conduit is to enclose and protect the insulation on the wires from becoming damaged. However, it has been determined that in some circumstances, the insulation on the wires becomes damaged by contact with a relatively sharp edge at the exposed corner of the connector. This is especially true when the wires passing through the connector are then bent for attachment to devices in the service box, e.g. circuit breakers. Either due to vibration or simply the pressure of the bent wire pressing against the inner edge of the connector, the insulation may be abraded, resulting in a short circuit. To overcome this, dangerous and expensive problem, the National Electrical Code requires the use of a protective bushing at the open end of the connector to prevent the wire's insulating jacket from contacting the connector. This insulating bushing is generally a plastic ring with internal threads for engagement with external threads on the connector. The bushing must be assembled to the connector before the wires are pulled through.
While the National Electrical Code regulation theoretically corrects the problem outlined above, like many such well-intentioned requirements, this one is not always complied with. For various reasons, the required bushing is not always installed. Omission of the bushing is likely to be discovered by an electrical inspector who will require the installer to correct the omission before certifying the electrical work. Correction at this stage involves disconnecting the wires from the apparatus in the service box, passing the protective bushing over the wires and onto the connector threads and reconnecting the wires. This involves a substantial amount of added work. In order to avoid the extra work this late installation entails, some contractors have resorted to cutting the ring bushing to create an opening, and wrapping the split bushing around the wires to assemble to the connector. This practice is dangerous and against the Code regulations. Thus a need exists to allow a protective bushing to be installed without disconnecting already attached wires.